Article identification systems are well known and are used in a variety of applications to prevent unauthorized access to physical locations, electronic data etc. or to ensure the validity of articles. For example, systems are known in which re-writable digital information is encoded into a magnetic marker element by creating adjacent regions along the magnetic marker element with alternating directions of remnant magnetization. The encoded digital information can subsequently be read from the marker element using a magnetic reader that includes a solenoid coil to pick up a magnetic signal induced by the regions of alternating remnant magnetization as the marker element is moved past the magnetic reader. Systems of this kind have been widely used to identify plastic cards such as credit and debit cards and many types of paper tickets. The magnetic element is typically in the form of a stripe and is commonly made from particulate or continuous magnetic media with coercivity greater than approximately 25 kA/m (300 Oe).
Other article identification systems based on volatile magnetic components have been proposed (see for example, International PCT Application Publication No. WO 98/13708, U.K. Patent No. 2349049, International PCT Application Publication No. WO 08/020148, U.S. Pat. No. 6,204,766, European Patent No. 0839330, European Patent No. 0295085, and U.S. Pat. No. 5,729,201, which are all incorporated herein by reference).
Other systems are known to prevent the unauthorized recording or modification of encoded data, as in security applications. In particular, access control systems are known where discrete magnetic Wiegand wire segments are assembled by a mechanical process into door-access key cards. When such a key card is swept past a suitable reader, the relative locations of the wire segments are decoded as they pass in proximity to one or more magnetic excitation zones and one or more magnetic pickup heads in the reader, and the resulting decoded data is used to identify the key card. To ensure an adequate pick-up signal, the wire segments are commonly made from bi-stable magnetic wire with a switching field near 2 kA/m (25 Oe) (see for example, U.S. Pat. No. 3,820,090, which is incorporated herein by reference). Security against counterfeiting of the key cards is provided by two main mechanisms: 1) the wire segments provide a magnetic response which is sufficiently distinct as to permit the reader to differentiate such wire segments from other types of magnetic materials more generally available; and 2) physical placement of the wire segments requires relatively high precision, and processes for such wire segment placement are not easily developed.
In addition to the systems described above, which use semi-hard magnetic materials, non-volatile soft-magnetic data markers have been considered (see for example, International PCT Application Publication No. WO 00/10123, International PCT Application Publication No. WO 99/67099, International PCT Application Publication No. WO 01/26049, U.S. Pat. No. 6,289,141, International PCT Application Publication No. WO 03/017192, European Patent Application No. 1039412, U.S. Pat. Nos. 6,144,300, 5,965,214, 5,538,803, and 5,821,859, which are all incorporated herein by reference), as have readers for such data markers (see for example, International PCT Application Publication No. WO 98/15851, U.K. Patent No. 2349051, International PCT Application Publication No. WO 01/13321, U.S. Pat. No. 6,323,770, and International PCT Application Publication No. WO 01/11541, which are all incorporated herein by reference), and combined systems of data markers and readers (see for example, International PCT Application Publication No. WO 96/31790, International PCT Application Publication No. WO 99/35610, International PCT Application Publication No. WO 02/084608, U.S. Pat. No. 7,320,433, European Patent No. 0713195, U.S. Pat. Nos. 5,175,419, and 5,204,526, which are all incorporated herein by reference).
Although various article identification systems and readers therefor have been considered, improvements are desired. It is therefore an object to provide a novel article identification reader, a marker element for article identification and a method of article identification.